It is known to make pressurized-water, boiling water, and pressurized-gas nuclear reactors with a shield surrounding the pressurized core, in order to protect the surroundings should the core burst. As a rule it has been found necessary to provide an inspection cavity between the pressurized core and the burst shield. This inspection cavity is used for a removable filling in order to reduce the burst way to zero. With the burst shield of the cited application, for example, the zero-path filling of the inspection cavity is comprised of cast-iron segments, which are put in place and lifted out by removing the burst shield cover.
Although this has given satisfactory results, it requires special fitting work and placing and lifting of the cast-iron segments is a rather considerable expenditure. In addition accurate computations of thermal expansion for dimensioning the cast-iron segments are necessary in order to assure the reduction of the free burst path to zero or practically to zero. Moreover it is important that the pressurized nuclear reactor core does not receive uncontrolled stresses due to pressures caused by thermal expansion of the cast-iron segments.